In a manufacturing line of semiconductor substrates, thin-film substrates and the like, in order to maintain and improve the yield of products, inspection of a defect existing on the surface of the semiconductor substrates, the thin-film substrates and the like is performed. As prior arts of the defect inspection, JP-A-8-304050 (Patent Literature 1), JP-A-2008-268140 (Patent Literature 2) and the like are known.
The Patent Literature 1 describes that “the same defect is illuminated plural time in one inspection by an illumination optical system which makes linear illumination and a detection optical system which divides an area to be illuminated by a line sensor and detects a defect and scattered light therefrom is added to thereby improve the detection sensitivity”.
The Patent Literature 2 describes that “2n APD's corresponding to laser light bands are arranged linearly” and “proper pairs of the 2n APD's are combined to calculate differences in output signals of the combined paired APD's, so that noise due to reflected light is erased and defect pulse for scattered light is outputted”.